A Milpitas man has been convicted of killing his girlfriend’s dog with a hammer and could be sentenced to life in prison for the death of the elderly cocker spaniel.

Santa Clara County Superior Court Judge Jerome E. Brock still must decide if the conviction of Alex Castro, 48, on charges of felony animal cruelty and use of a deadly weapon will count as a third strike, which could send the drywall finisher to prison for 35 to 37 years to life.

“Somebody with the violent history he has is exactly who the voters were thinking of” with the “three strikes” law, said Deputy District Attorney Kevin Smith, who prosecuted the case.

A jury returned the guilty verdict on Monday,

Before he was charged with killing 10-year-old Copper, a cocker spaniel that belonged to his girlfriend Joanie Gonzalez, with a ball-peen hammer in 2007, Castro had a felony record that included convictions for assault with a deadly weapon and battery resulting in serious injuries.

Castro and Gonzalez were sharing a trailer in Milpitas when Copper was killed. The dog apparently was not housebroken and Castro made the dog stay outside, prompting numerous complaints from neighbors about Copper’s barking.

Castro denied killing the dog, suggesting he had been hit by a car. But when he took the stand in his own defense, Castro admitted to moving the dog’s body four times after finding Copper dead. Those moves corresponded to areas where Castro tried to clean up the dog’s blood, the prosecutor said.

The jury returned its verdict on Monday.

Castro still faces a separate hearing on charges of soliciting to prevent a witness from testifying in the case.

After a probation report is submitted to the court on July 24, a hearing will be held before Judge Brock prior to sentencing. Brock has the discretion to determine if the three strikes law applies to Castro.